This invention relates to food preparation ovens and in particular to food preparation ovens for preparing pizza and similar types of food products. Specifically the invention relates to an impingement oven wherein food products are baked or cooked by means of jets of hot gaseous fluid such as hot air and wherein the hot air jets are impinged directly upon localized areas of the food products.
In the fast food restaurant business, it is both important that food is prepared very quickly and that the amount of kitchen space required for food preparation is minimized so that the productivity per square foot of kitchen floor space is maximized. It is, therefore, desired to provide an efficient compact oven to thereby maximize the productivity of restaurant kitchen floor space.
Advances have been made in the speed at which fast foods such as pizzas may be prepared by providing impingement ovens wherein a conveyor transports food products through an oven cavity. A plurality of duct fingers are disposed above and below the conveyor for forming a plurality of columnated jets of heated air and for impinging the jets directly against discreet points of the food products as they travel slowly through the oven cavity. Such ovens generally include a single burner for heating the air and a single fan for distributing the air through a plenum to the impingement fingers. The time required for preparing food products in such impingement ovens is substantially less than the time required for preparing food products in conventional prior art convection ovens. U.S. Pat. Ser. No. 4,556,043, which is assigned to the assignee of the present invention, discloses such an impingement oven which has been commercially very successful.
It is important in these types of impingement ovens that the velocity of the impingement air jets is sufficiently high to cause rapid thermal energy transfer to the food products. Furthermore, it is important to provide proper air pressure distribution in the plenum and the impingement fingers to generate an even flow of air through the impingement fingers thereby forming evenly distributed impingement jets.
In conventional impingement ovens, the air, after its distribution through the plenum and the impingement fingers, flows back to the fan by way of the top, bottom, and sides of the oven. Some of the air escapes from the oven by way of the openings in the side walls of the oven through which the conveyor extends. It is therefore desired to provide an impingement oven wherein the return air flows through the center of the oven. It is furthermore desired to provide an impingement oven of reduced height so that a greater number of ovens may be stacked on top of each other than was possible with prior art ovens to increase the productivity of the kitchen floor space without sacrificing food preparation time or food quality.
In impingement ovens, it is necessary to provide a large air mass flow rate to maximize thermal energy transfer. Axial fans have been commonly used in impingement ovens because of their superior air movement characteristics since they provide high velocity, low pressure air flow. The height of prior art impingement ovens has been dictated by the size of the axial fans which have been used with such ovens. Therefore, one potential approach to reducing the oven height is to use multiple fans, whereby each fan would have a smaller diameter than the single fan which is used with prior art impingement ovens. However, conventionally, the burners used in impingement type ovens have been designed so that a burner can only supply thermal energy to a single air plenum and a single fan. Therefore, if burners of conventional design were used, multiple fan impingement ovens would require multiple burners. This, of course, would entail considerable cost for supplying multiple burners as well as a complex control system to control such multiple burners. It is, therefore, desired to provide an impingement oven which uses multiple fans but only a single burner.